# Possibility of single stroke engine.

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#### Swampyankee

##### Well-Known Member
I think that Brown Boveri built a few. Combustion was not in the rotor.
I think they built some wave rotor machines as superchargers. I've not paid much attention to wave rotors -- sometimes they seemed like a solution in search of a problem.

#### wsimpso1

##### Super Moderator
Staff member
Log Member
Looking into for the future of building my own plan. I like the common engines but I just want something unique per say. Would a single stroke engine be possible in the case that fuel and air would be pre mixed and injected just before top dead center then ignited and burned for the down stroke/combustion. Before starting what would be the new compression stroke a valve would open pulling a strong enough vacuum to pull the exhaust and close letting the piston rise to another spot before top dead and open a valve with the fuel and air mixture already mixed and under pressure for the combustion to be pushed into the cylinder to be burned next?
In our customary two- and four-strokes, the engine is the big pump, moving the spent charge out, moving the new charge in, compressing it nearly adiabatically, then after the fuel is burned, expanding the charge nearly adiabatically.

Your idea, well, it is still a two stroke (once down, then back up per cycle, two strokes). Now let's get into the other topics...
• The compressor has to produce gas volumes and pressures in the combustion chamber similar to what we get now.
• When you open the intake valve with the piston near TDC, the compressed air will expand across the valve, losing some energy. This is pumping losses;
• You will have to make the compressor bigger than the combustion chamber system to actually get to efficient combustion chamber pressures;
• The vacuum pump for the exhaust will have to handle more volume than at the intake. You added fuel to the air that went in and burned it, so now you have more mass of gas, converted to smaller molecules and so converted to more moles than went in making for more volume at atmospheric pressure, raised its temperature making for more volume. The pump won't have to be as strong, but it sure will have more volume;
• So, instead of letting a single pumping chamber do the pumping in and compressing and pumping out, you will have a charge pump that goes to really high pressures, a power cylinder, and a really large evacuation pump and all three have to run in concert to make the engine run.
Wanna bet you will need to run it up into the operating range just to get it to be self sustaining? If idle power is 40% rpm, like jet engines, you will have fun managing this beast on the ground because the prop is then running at 16% torque and thrust when you are trying to taxi...

Speaking of jet engines, they do run a big compressor on the inlet, but they do not have a evacuator on the outlet and burn fuel continuously...

If you want to play with single stroke heat engines, the only ones I know of are kind of difficult to operate continuously. They throw away the piston on each stroke, burn fuel that runs around $20 a pound, get dirty to the point of needing cleaning every couple hundred firing strokes... Go a little more primitive and they become two-strokes, as the piston has to go both ways down the bore before being lost and they need cleaning about every 3-10 firing strokes. We are talking guns here... Billski #### pictsidhe ##### Well-Known Member I just read back and saw a posts that I missed, I think we're getting trolled... #### BBerson ##### Well-Known Member HBA Supporter Could inject liquid air and fuel at TDC (and BDC if double acting). Or just at TDC with the return stroke doing nothing but some lubrication. #### mcrae0104 ##### Well-Known Member HBA Supporter Log Member I just read back and saw a posts that I missed, I think we're getting trolled... I don't know about that, but a one-stroke engine sounds a lot like one hand clapping... #### Swampyankee ##### Well-Known Member In our customary two- and four-strokes, the engine is the big pump, moving the spent charge out, moving the new charge in, compressing it nearly adiabatically, then after the fuel is burned, expanding the charge nearly adiabatically. Your idea, well, it is still a two stroke (once down, then back up per cycle, two strokes). Now let's get into the other topics... • The compressor has to produce gas volumes and pressures in the combustion chamber similar to what we get now. • When you open the intake valve with the piston near TDC, the compressed air will expand across the valve, losing some energy. This is pumping losses; • You will have to make the compressor bigger than the combustion chamber system to actually get to efficient combustion chamber pressures; • The vacuum pump for the exhaust will have to handle more volume than at the intake. You added fuel to the air that went in and burned it, so now you have more mass of gas, converted to smaller molecules and so converted to more moles than went in making for more volume at atmospheric pressure, raised its temperature making for more volume. The pump won't have to be as strong, but it sure will have more volume; • So, instead of letting a single pumping chamber do the pumping in and compressing and pumping out, you will have a charge pump that goes to really high pressures, a power cylinder, and a really large evacuation pump and all three have to run in concert to make the engine run. Wanna bet you will need to run it up into the operating range just to get it to be self sustaining? If idle power is 40% rpm, like jet engines, you will have fun managing this beast on the ground because the prop is then running at 16% torque and thrust when you are trying to taxi... Speaking of jet engines, they do run a big compressor on the inlet, but they do not have a evacuator on the outlet and burn fuel continuously... If you want to play with single stroke heat engines, the only ones I know of are kind of difficult to operate continuously. They throw away the piston on each stroke, burn fuel that runs around$20 a pound, get dirty to the point of needing cleaning every couple hundred firing strokes... Go a little more primitive and they become two-strokes, as the piston has to go both ways down the bore before being lost and they need cleaning about every 3-10 firing strokes. We are talking guns here...

Billski
Well, the first internal combustion engines did use gunpowder...

#### Tiger Tim

##### Well-Known Member
single stroke engine would have to fire at TDC and BDC, no?
Even then the piston has to come back and get reset for the cycle, meaning the cycle has to have an even number of strokes. A guess a turbine would be a sort of one-stroke engine?

#### TFF

##### Well-Known Member
A turbine is a constant stroke engine. I figure a rocket would be the closest by definition to one stroke.

#### mm4440

##### Well-Known Member
A cannon is a single stroke engine if you do not consider loading it a stroke. Throwing the piston away each power stroke makes it impractical.

#### choppergirl

##### Banned
I do at least 3 impossible things before breakfast.

A cylinder, capped on both ends, with a spark plug on both ends, and a piston in center.

Blast on left side, piston moves right, and compresses mixture on right.

Blast then on right side, piston moves left, and compresses mixture on left.

Repeat, over and over again, back and forth. Power on all strokes with one piston.

Blue dot, in case you didn't guess, extends out slot in side of cylinder barrel on both sides and is where you extract power from.

Of course, add cooling fans, or water jacket, ports for premix (lubricating oil and fuel), carb, exhaust, and other supporting hardware and electrics, not drawn on purpose, so that you can see piston action and motion without any more chartfunk.

I wouldn't doubt some Choo Choo Trains in the far distant past used this design, only with steam pressure, not dino juice explosions. So keep that in mind before you run down to the patent office with my diagram in hand still hot off your lasar printer drum.

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#### nerobro

##### Well-Known Member
Log Member
Still "at least" two stroke. Opposed piston engines have been built.

#### mm4440

##### Well-Known Member
Search free piston engines.

#### Swampyankee

##### Well-Known Member
Search “double-acting engine”

#### mcrae0104

##### Well-Known Member
HBA Supporter
Log Member
Blast on left side, piston moves right, and compresses mixture on right.

Blast then on right side, piston moves left, and compresses mixture on left.

Repeat, over and over again, back and forth. Power on all strokes with one piston.
Blasting suffers considerably without an intake stroke. But perhaps this is an opposed two stroke?

#### pictsidhe

##### Well-Known Member
I do at least 3 impossible things before breakfast.

A cylinder, capped on both ends, with a spark plug on both ends, and a piston in center.

Blast on left side, piston moves right, and compresses mixture on right.

Blast then on right side, piston moves left, and compresses mixture on left.

Repeat, over and over again, back and forth. Power on all strokes with one piston.

Blue dot, in case you didn't guess, extends out slot in side of cylinder barrel on both sides and is where you extract power from.

Of course, add cooling fans, or water jacket, ports for premix (lubricating oil and fuel), carb, exhaust, and other supporting hardware and electrics, not drawn on purpose, so that you can see piston action and motion without any more chartfunk.

I wouldn't doubt some Choo Choo Trains in the far distant past used this design, only with steam pressure, not dino juice explosions. So keep that in mind before you run down to the patent office with my diagram in hand still hot off your lasar printer drum.
That's a twin cylinder engine with connected pistons. Each half fires for half the time. It spends the other time going the other way.
That arrangement is called a 'double acting cylinder' very popular in hydraulics and pneumatics.
A great number of steam engines used double acting cylinders.